Recently, a nonaqueous electrolyte secondary battery, such as a lithium ion secondary battery, has substituted for a conventional secondary battery, such as lead secondary battery, nickel cadmium secondary battery and nickel hydride secondary battery, and plays the principle role in a small secondary battery for electronics due to its high power density.
The nonaqueous electrolyte secondary battery may be used in a single in mobile phone, etc., and in multiply used in laptop computer, automobile, etc. When properties such as charging capacity and discharging capacity between cells are varied in case of using in multiple, and as a result, a part of batteries is subject to large charging load and discharging load, there may arise such problems that dramatically reducing lifetime.
An electrode of nonaqueous electrolyte secondary battery is obtained by pressure treatment after applying a slurry to a collector and drying the slurry, wherein the slurry comprises active material and binding agent, and optionally conductive agent and thickener dispersed and mixed to organic solvent or water (herein after referred as “slurry for electrodes”). When stability of the slurry for electrodes is insufficient, a thickness and a density of electrode becomes ununiformity due to occurrence of aggregation and depression of the active material at the time of preservation and coating. The uniformity of the electrode like this causes variability of properties such as charging capacity and discharging capacity between cells produced by using them.
To solve such a problem, in Patent Document 1, it has been proposed a positive paste (slurry for electrodes) which is kneaded and dispersed by using surface modified conductor with additional a specific dispersing agent. Also, in Patent Document 2, it has been proposed that a producing method for slurry for electrodes comprising preliminarily producing paste by kneading plasticizing agent, active material and conductive agent preliminarily, then, adding binder composition wherein binding agent is dispersed in carrier medium and kneaded further. Although slurry for electrodes having advantageous stability can be obtained by either methods, there was a problem that productivity is reduced due to complicated producing process.    Patent Document 1: Japanese Patent Laid Open No. 2001-23613    Patent Document 2: Japanese Patent Laid Open No. 2000-12001